Ryan T. Borne

Outcomes Among Older Patients Receiving Implantable Cardioverter-Defibrillators for Secondary Prevention: From the NCDR ICD Registry

BACKGROUNDnClinical trials of implantable cardioverter-defibrillators (ICDs) for secondary prevention of sudden cardiac death were conducted nearly 2 decades ago and enrolled few older patients.nnnOBJECTIVESnThis study assessed morbidity and mortality of older patients receiving ICDs for secondary prevention in contemporary clinical practice.nnnMETHODSnWe identified 12,420 Medicare beneficiaries from the National Cardiovascular Data Registry ICD Registry undergoing first-time secondary prevention ICD implantation between 2006 and 2009 in 956 U.S. hospitals. Risks of death, hospitalization, and admission to a skilled nursing facility (SNF) were assessed over 2 years in age strata (65 to 69, 70 to 74, 75 to 79, andxa0≥80 years of age) using Medicare claims. The adjusted association between age and outcomes was evaluated using multivariable models.nnnRESULTSnThe mean age was 75 years at the time of implantation; 25.3% werexa0<70 years of age and 25.7% were ≥80xa0years of age. Overall, the risk of death at 2 years was 21.8%, ranging from 14.7% among thosexa0<70 years of age to 28.9% among thosexa0≥80 years of age (adjusted risk ratio [aRR]: 2.01; 95% confidence interval [CI]: 1.85 to 2.33; pxa0for trend <0.001). The cumulative incidence of hospitalizations was 65.4%, ranging from 60.5% in thosexa0<70 years of age to 71.5% in thosexa0≥80 years of age (aRR: 1.27; 95% CI: 1.19 to 1.36; p for trendxa0<0.001). The cumulative incidence of admission to a SNF ranged from 13.1% among thosexa0<70 years of age to 31.9% among those ≥80xa0yearsxa0of age (aRR: 2.67; 95% CI: 2.37 to 3.01; p for trendxa0<0.001); SNF admission risk was highest in the first 30xa0days.nnnCONCLUSIONSnAlmost 4 in 5 older patients receiving a secondary prevention ICD survives at least 2 years. High hospitalization and SNF admission rates, particularly among the oldest patients, identify substantial care needs after device implantation.

Identification and Characterization of Sites Where Persistent Atrial Fibrillation Is Terminated by Localized Ablation

Background: The mechanisms by which persistent atrial fibrillation (AF) terminates via localized ablation are not well understood. To address the hypothesis that sites where localized ablation terminates persistent AF have characteristics identifiable with activation mapping during AF, we systematically examined activation patterns acquired only in cases of unequivocal termination by ablation. Methods and Results: We recruited 57 patients with persistent AF undergoing ablation, in whom localized ablation terminated AF to sinus rhythm or organized tachycardia. For each site, we performed an offline analysis of unprocessed unipolar electrograms collected during AF from multipolar basket catheters using the maximum –dV/dt assignment to construct isochronal activation maps for multiple cycles. Additional computational modeling and phase analysis were used to study mechanisms of map variability. At all sites of AF termination, localized repetitive activation patterns were observed. Partial rotational circuits were observed in 26 of 57 (46%) cases, focal patterns in 19 of 57 (33%), and complete rotational activity in 12 of 57 (21%) cases. In computer simulations, incomplete segments of partial rotations coincided with areas of slow conduction characterized by complex, multicomponent electrograms, and variations in assigning activation times at such sites substantially altered mapped mechanisms. Conclusions Local activation mapping at sites of termination of persistent AF showed repetitive patterns of rotational or focal activity. In computer simulations, complete rotational activation sequence was observed but was sensitive to assignment of activation timing particularly in segments of slow conduction. The observed phenomena of repetitive localized activation and the mechanism by which local ablation terminates putative AF drivers require further investigation.

Survival After Secondary Prevention Implantable Cardioverter-Defibrillator Placement : An Analysis From the NCDR ICD Registry

OBJECTIVESnThis study sought to define the characteristics and risks of death of patients receiving a physician-designated secondary prevention implantable cardioverter-defibrillator (ICD) in contemporary clinical practice.nnnBACKGROUNDnData on utilization and outcomes of ICDs for the secondary prevention of sudden cardiac death (SCD) are limited.nnnMETHODSnPatients enrolled in the National Cardiovascular Data Registrys (NCDR) ICD Registry from 2006 to 2009 with a physician-designated secondary prevention indication for ICD implantation were identified and linked to the Social Security Death Master File. Those patients with a history either of tachycardic arrest or sustained ventricular tachycardia (SCD/VT) or of syncope without SCD/VT were included. Kaplan-Meier survival analysis was used to assess mortality. Cox proportional hazards survival modeling was used to assess the risk of death in these groups, adjusting for patient characteristics.nnnRESULTSnIn the study cohort of 46,685 patients (mean age 66 ± 14 years, 73.5% male, 85% white), 78% had SCD/VT and 22% had syncope. Overall mortality was 10.4% at 1 year and 16.4% at 2 years. Compared with patients having SCD/VT, the adjusted hazard of death at 1 year was lower in the patients having syncope (hazard ratio: 0.89; 95%xa0confidence interval: 0.83 to 0.96) but was not significantly different by 2 years (hazard ratio: 0.96; 95% confidence interval: 0.90 to 1.01).nnnCONCLUSIONSnNearly 9 of 10 patients receiving a secondary prevention ICD in clinical practice are alive 1 year after implantation. The risk of death varies by indication and is highest among patients who survive SCD or sustained VT inxa0thexa0first year after device implantation.

Use of Tissue Electric and Ultrasound Characteristics to Predict and Prevent Steam-Generated Cavitation During High-Power Radiofrequency Ablation

OBJECTIVESnGiven a paucity of data, the aim of this study was to define predictors of steam pops (SPs) during open-irrigated radiofrequency ablation (RFA).nnnBACKGROUNDnSPs during RFA can lead to dire consequences, including perforation and stroke.nnnMETHODSnIn an exxa0vivo bovine myocardium model, open-irrigated RFA was applied at 50 W for 60 s; intracardiac echocardiographic images for RFA with and without SPs was compared. Using an inxa0vivo porcine model, open-irrigated RFA was applied at 50 W for 60 s, and RFA parameters of SPs were analyzed. A retrospective analysis was performed of recorded SPs during clinical ablation procedures over a 1-year period.nnnRESULTSnFor RFA SPs, there was 32% greater intracardiac echocardiographic tissue echogenicity than for RFA without SPs (pxa0< 0.001). In addition, RFA SPs had more rapid increases of tissue echogenicity, particularly in the last 5 s before SPs. Compared with RFA without SPs, RFA SPs had larger impedance reductions (33.0 ± 16.0 Ω vs. 23.0 ± 10.8 Ω; pxa0=xa00.032). SPs were also associated with more rapid initial impedance reduction (1.40 Ω/s vs. 0.38 Ω/s for RFA withoutxa0SPs; pxa0= 0.001). Clinical SPs during ablation procedures had a significantly faster impedance reduction during the first 5 s of ablation compared with matched control ablations (15.7 ± 6.7 Ω vs. 8.1 ± 4.7 Ω; pxa0< 0.0001).nnnCONCLUSIONSnCertain echocardiographic and biophysical parameters during open-irrigated RFA are associated withxa0increased SP risks. These include greater tissue echogenicity, larger total impedance reduction, rapid rate ofxa0initialxa0impedance reduction, and rapid increase in tissue echogenicity.

Longer Duration Versus Increasing Power During Radiofrequency Ablation Yields Different Ablation Lesion Characteristics

OBJECTIVESnThe goal of this study was to characterize differences in ablation lesions with varying radiofrequency ablation (RFA) power and time.nnnBACKGROUNDnIncreasing power delivery or prolonging duration can improve the efficacy of RFA. However, the extent to which ablation lesion characteristics change, based on varying degrees of power and duration, is unknown.nnnMETHODSnAn exxa0vivo model consisting of viable bovine myocardium in a circulating warmed saline bath was used. An open irrigated RFA catheter was positioned with 10 g of force in the perpendicular position, and RFA was delivered at powers of 20, 30, 40, and 50 W and for various time intervals, up to a total of 90 s, at each power. An inxa0vivo porcine thigh preparation model was used to perform RFA at 50 W for 5 s and 20 W for 30 s. Lesion volumes were analyzed.nnnRESULTSnGreater power delivery and longer radiofrequency time increased ablation lesion size. However, compared with a proportional change in radiofrequency duration, the same proportional increase in power produced a significantly larger lesion volume (pxa0< 0.01). For inxa0vivo models, 50 W/5 s ablation lesions yielded similar volumes but significantly less depth than 20 W/30 s ablation lesions. Peak temperatures were not significantly different at 2 and 4 mm with 50 W/5 s versus 20 W/30 s.nnnCONCLUSIONSnVarying power and duration will confer different ablation lesion characteristics that can be tailoredxa0according to the substrate/anatomy that is being ablated. This phenomenon has important implications during catheter ablation.

Spatial relationship of sites for atrial fibrillation drivers and atrial tachycardia in patients with both arrhythmias

INTRODUCTIONnAtrial fibrillation (AF) often converts to and from atrial tachycardia (AT), but it is undefined if these rhythms are mechanistically related in such patients. We tested the hypothesis that critical sites for AT may be related to regional AF sources in patients with both rhythms, by mapping their locations and response to ablation on transitions to and from AF.nnnMETHODSnFrom 219 patients undergoing spatial mapping of AF prior to ablation at 3 centers, we enrolled 26 patients in whom AF converted to AT by ablation (n=19) or spontaneously (n=7; left atrial size 42±6cm, 38% persistent AF). Both atria were mapped in both rhythms by 64-electrode baskets, traditional activation maps and entrainment.nnnRESULTSnEach patient had a single mapped AT (17 reentrant, 9 focal) and 3.7±1.7 AF sources. The mapped AT spatially overlapped one AF source in 88% (23/26) of patients, in left (15/23) or right (8/23) atria. AF transitioned to AT by 3 mechanisms: (a) ablation anchoring AF rotor to AT (n=13); (b) residual, unablated AF source producing AT (n=6); (c) spontaneous slowing of AF rotor leaving reentrant AT at this site without any ablation (n=7). Electrogram analysis revealed a lower peak-to-peak voltage at overlapping sites (0.36±0.2mV vs 0.49±0.2mV p=0.03).nnnCONCLUSIONSnMechanisms responsible for AT and AF may arise in overlapping atrial regions. This mechanistic inter-relationship may reflect structural and/or functional properties in either atrium. Future work should delineate how acceleration of an organized AT may produce AF, and whether such regions can be targeted a priori to prevent AT recurrence post AF ablation.

Red Alert: Infrared Thermography for Esophageal Monitoring

See Article by Daly et al nnPulmonary vein isolation (PVI) remains the cornerstone for catheter ablation of atrial fibrillation (AF).1 Although atrioesophageal fistula is a known but rare complication, with an estimated incidence of <0.25% after conventional radiofrequency ablation, it is highly morbid and often fatal.2–4 Given that ablation of AF is an increasingly used modality of treatment, and ablation over the posterior wall is an essential and unavoidable aspect of catheter ablation of AF, the risk of atrioesophageal fistula will continue to be a feared complication in the care of these patients.nnMultiple methods have been developed and used with the intent of reducing esophageal injury (Figure). Ablation strategies have been used to avoid ablation directly over the esophagus, including visualization of the esophagus based on computerized tomography, topographical tagging with an electroanatomic mapping system, barium paste, and intracardiac echocardiography. However, the esophagus can change position and, at times, ablation over the esophagus is necessary, making these strategies difficult and requiring continuous imaging or visualization to account for motion. Higher power and greater depth of tissue heating are associated with increased risk of esophageal injury; therefore, reduction in power, ablation duration, and contact force has been used to reduce depth of ablation lesions. Active cooling of the esophagus, mechanical movement, and pharmacological prophylaxis with use of proton pump inhibitors are other methods that have been used, but large-scale safety studies are lacking, and these all remain unproven.5–7nnnnFigure. nStrategies of reducing esophageal injury during catheter ablation . 3D indicates 3-dimensional.nnnnFinally, luminal esophageal temperature monitoring has been performed with the intent of identifying heating within the esophagus. Using this approach, ablation can be interrupted if temperature rises, typically with a cutoff of >1 to 2°C rise or above an absolute value of 39 …

Double jeopardy: long QT3 and Brugada syndromes

Mutations in the SCN5A gene are linked to both the long QT syndrome 3 and Brugada syndrome with few reports describing an overlapping phenotype. We present a unique case and discuss clinical considerations of a patient concurrently exhibiting such conditions with genetic analysis confirming an SCN5A mutation.

Intra-atrial Reentrant Tachycardia in Complete Transposition of the Great Arteries Without Femoral Venous Access.

Catheter ablation for patients with transposition of the great arteries (d-TGA) requires multiple considerations and careful preprocedural planning. Knowledge of the patients anatomy and surgical correction, in addition to electroanatomic mapping and entrainment maneuvers, are important to identify and successfully treat arrhythmias. This case was unique in that the lack of femoral venous access required transhepatic venous access and bidirectional block was attained with ablation lesions along the cavotricuspid isthmus on both sides of the baffle.